Cystic fibrosis related diabetes (CFRD) is one of the most significant co-morbidities in Cystic Fibrosis (CF), affecting almost half of patients over 30 years of age. CFRD is associated with a high morbidity and mortality. Insulin secretory defects are inherent to CF, with diminished and/or delayed insulin responses to oral glucose demonstrated in CF patients both with and without diabetes. Because the islet mass is generally retained in CF, therapies to restore insulin secretion will significantly reduce the incidence of CFRD and thus morbidity and mortality. However, there are no such therapies, because the mechanisms underlying kinetically altered insulin secretion in CF are not known. Oxidative stress and fatty acid perturbations have well-established roles in the pathophysiology of lung disease in CF and type 2 diabetes mellitus, but have not been studied in CFRD. Cystic fibrosis transmembrane conductance regulator (CFTR)-knockout pig and ferret models developed at the University of Iowa have multi-organ disease similar to humans with CF. However, the evolution to CFRD and its severity are different between the two models. At birth, both models have abnormal insulin secretion, but the concomitant exocrine pancreatic disease is mild in CF ferrets and advanced in CF pigs. Pancreatic disease advances rapidly in CF ferrets after birth and they develop progressive hyperglycemia, whereas the pancreatic disease progression is slower in CF pigs and they do not develop hyperglycemia as adults. At birth, CF pigs and ferrets have an imbalance of polyunsaturated fatty acids (PUFA) similar to patients with CF and have markers of pancreatic oxidative stress. Given their varying degrees of exocrine pancreatic disease at birth, divergent evolution to CFRD, fatty acid alterations similar to CF humans and pancreatic oxidative stress, CF ferret and porcine models provide unique and complementary opportunities to investigate the pathogenesis of insulin secretion defects in CF. We hypothesize that the oxidative stress and CF-related PUFA imbalance are key mechanisms that underlie the impaired insulin secretion in CF. We will test this hypothesis in both CF pig and ferret models with the following specific aims: (1) Determine the effect of reactive oxygen species (ROS) and oxidative stress on insulin secretion in vivo by the CF pancreas; (2) Determine the effect of CF-related PUFA imbalance on insulin secretion in vivo by the CF pancreas; (3) Determine the effect of fatty acid alterations and ROS on insulin secretion by isolated islets. The first aim wil determine the relationship between increased levels of ROS, oxidative stress, and antioxidant capacity in CF pig and ferret pancreas along with correlating the severity of redox changes with insulin secretion. The second aim will determine whether correcting CF-related PUFA imbalance will restore the !-cell function in CF pancreas. The third aim will ! examine the extent to which the fatty acid alterations and oxidative stress are intrinsic mechanisms of impaired insulin secretion in CF islets. The objective of this application is to identify oxidative stress and CF-related PUFA imbalance as key pathways in the pathogenesis of CFRD.